As one of techniques in the above field, there is heretofore known a flat type resolver disclosed in for example Patent Document 1 listed below. This flat type resolver includes a stationary-side core, a moving-side core, and a plurality of sheet coils of a multi-X type provided on a main surface of the stationary-side core. Further, connecting wires that connect the sheet coils with each other are connected so as to extend for a nearly one circle around the stationary-side core.
There is also known a sheet-coil type resolver disclosed in Patent Document 2 listed below. This resolver includes an excitation phase coil and a detection phase coil. The excitation phase coil is provided with a spiral coil (a planar coil) on a main surface of an insulation sheet layer and a spiral coil (a planar coil) on a back surface to be wound in a reverse direction when viewed from the same direction as the main surface. The detection phase coil is provided with a spiral coil (a planar coil) on a main surface of an insulation sheet layer and a spiral coil (a planar coil) on a back surface to be wound with an electric phase difference of 90° from the main-surface spiral coil (the planar coil). The excitation phase coil and the detection phase coil are placed to face each other with a gap therebetween so that they are allowed to move relatively. Herein, each spiral coil of the excitation phase coil is made in a manner that circular-arc conductors and straight conductors are joined or circular-arc conductors or straight conductors are connected into a spiral form. Each spiral coil of the detection phase coil is made in a manner that half sine-wave-shaped conductors and circular-arc or straight conductors are serially connected into a spiral form. In the spiral coils of the excitation phase coil or detection phase coil, wound in a reverse direction opposite to the spiral coils wound in a forward direction, outer circumferential ends of adjacent spiral coils are directly connected with each other while inner circumferential ends are connected with each other through connecting wires provided on different layers.
There is further known a sheet coil type resolver disclosed in Patent Document 3 listed below. This resolver is provided with two sheet coils each including a circular-disc like thin-film substrate on which a coil pattern is formed. These two sheet coils are placed to face each other with a gap therebetween. The two sheet coils include a single-phase coil pattern made of a good conductive foil wound in a spiral shape turned in a reverse direction from the center of the substrate and a double-phase coil pattern including spirally wound coil patterns arranged on a main surface and a back surface of a thin-film substrate with a phase displacement of an electrical angle of π/2 from each other. Outside the single-phase coil pattern, a transformer secondary pattern to supply excitation voltage to the single-phase coil pattern and a transformer primary pattern having the same pattern as the transformer secondary pattern are provided separately from the two sheet coils. Both the patterns are placed to face each other with a gap therebetween.